The overall objective of this proposed research is to establish the mechanisms responsible for the short-term hormonal regulation of hepatic glucose and fat synthesis. Studies will be conducted with isolated hepatocytes, cell-free extracts, and purified acetyl-CoA carboxylase. A number of CoA esters of hypolipidemic drugs will be synthesized. The specific aims include: to further clarify the mechanism responsible for glucagon inactivation and insulin activation of rat liver phosphofructokinase; to establish whether oleate inhibition of glycolysis is due to the conversion of phosphofructokinase into an inactive form by covalent modulation; to establish whether glucagon inhibition of glucose utilization by chicken hepatocytes is due to inactivation of phosphofructokinase; to determine whether lactate reversal of cyclic AMP inhibition of hepatic lipogenesis involves "protection" of acetyl-CoA carboxylase against inactivation by covalent modulation; to establish whether glucagon inhibition of fatty acid synthesis by chicken liver involves conversion of acetyl-CoA carboxylase into an inactive form of the enzyme; to establish whether 3H2O incorporation measures the true rate of fatty acid synthesis; to establish a method for determining the specific radioactivity of the cytosolic NADPH pool of hepatocytes incubated with 3H2O; to establish whether a number of hypolipidemic agents are converted to the CoA esters which in turn inhibit fatty acid synthesis by inhibition of acetyl-CoA carboxylase. The major working hypothesis is that glucagon and insulin regulate the capacity of the liver to synthesize glucose and fat by changing the phosphorylation state of the hepatic enzymes subject to covalent modulation. Hypolipidemic drugs such as 5-(tetra-decyloxy)-furoic acid which mimic in many ways the actions of glucagon on metabolic pathways are proposed to be enzymatically converted to CoA esters which also destroy the lipogenic climate of the liver by inhibition of acetyl-CoA carboxylase.